Volkswagen Introduces BlueMotionTechnologies Umbrella Brand for Fuel-Efficient, Low-Emissions Technologies; Previews Touareg Hybrid
|Prototype Touareg Hybrid. Click to enlarge.|
In the first part of 2009, Volkswagen will simultaneously bring three fuel-efficient Passat versions with low emissions to the market: the second generation of the Passat BlueMotion, the Passat BlueTDI and the Passat TSI EcoFuel. Volkswagen is presenting all three Passats under a new umbrella brand: BlueMotionTechnologies. This label covers all production-mature or near-production technologies and products that significantly reduce fuel consumption and CO2 emissions. Under the same label, Volkswagen is offering an initial look at the prototype of the new Touareg Hybrid.
The term BlueMotionTechnologies does not define a fixed set of technologies but a range of continually evolving solutions, currently including systems such as a new stop-start system, regenerative braking, SCR catalytic converter and the NOx storage catalytic converter, electric drive and hybrid systems.
|Powertrain of the Touareg Hybrid. Click to enlarge.|
Touareg Hybrid. Volkswagen is implementing a parallel hybrid drive on the future Touareg V6 TSI Hybrid. The Touareg Hybrid prototype is powered by a new 3.0-liter V6 TSI—a direct injection gasoline engine boosted by a mechanically-driven supercharger—in tandem with an electric motor and mated with a newly developed 8-speed automatic transmission. The hybrid offers all-wheel drive and 3.5 tonnes of towing capacity.
The V6 TSI on the Touareg prototype delivers 245 kW (329 hp) at 5,500 rpm. From its 2,995 cm3 displacement, it generates a maximum torque of 440 Nm (325 Nm) starting from 3,000 rpm. The V6 TSI makes use of a switchable engine water pump that remains off during the warm-up phase, ensuring rapid achievement of fuel efficient operation. The pump is integrated into the vehicle’s overall heat management system.
|Torque and power with and without maximum E-motor boost. Click to enlarge.|
The E-motor integrated between the V6 TSI and the 8-speed automatic transmission adds power of 38 kW (51 hp) and up to 300 Nm torque (221 lb-ft). In boosting mode—where maximum torque and power are required—the V6 TSI engine and the electric motor operate together to deliver temporary maximum power of 275 kW (369 hp) with a maximum torque of 550 Nm (406 lb-ft). In this case, the Touareg V6 TSI Hybrid prototype accelerates to 100 km/h in just 6.8 seconds.
Fuel consumption is expected to be less than 9.0L/100km (26 mpg US) for the full-size SUV—about a 25% improvement in city driving over a conventional gasoline SUV of the same size. VW engineers calculate an average savings of 17% in combined city, highway and freeway driving. Contributing to the decreased fuel consumption are a number of different systems and operating modes:
Stop-start. An integrated stop-start system significantly reduces fuel consumption, especially in urban driving.
Regenerative braking. During braking, the E-motor operates as a generator and recovers energy, which is then stored in the high voltage NiMH battery pack.
All-electric drive mode. The vehicle can operate on the electric motor alone at speeds of up to 50 km/h (31 mph), which reduces fuel consumption in city driving. In this case the V6 TSI is turned off, and it is disconnected from the transmission by a disengagement clutch. In this condition the Touareg V6 TSI Hybrid operates with zero emissions. Electric current flows from the battery to the E-motor via the power electronics which incorporates a pulse controlled inverter. On the later production version, there are also plans for a special E-switch that the driver can activate for pure electric driving.
Coasting mode. As soon as the driver removes his or her foot from the gas pedal, a clutch disengages the V6 TSI from the transmission. (The disengagement clutch and the E-motor are housed together in the 55 kg hybrid module integrated between the internal combustion engine and the automatic transmission.) This is even possible at higher speeds—in the later production version up to about 160 km/h (99 mph)—and therefore in freeway driving as well. This eliminates mechanical drag losses, which in turn makes the Touareg coast significantly better. The driver can convert this directly into improved fuel economy by adopting an anticipatory driving style.
Conventional ICE mode. When driving with just the internal combustion engine, there are two possible modes of operation. In the first case, the Touareg is driven like a conventional vehicle with the E-motor performing the function of a conventional 12 V alternator, which it replaces, to supply sufficient energy for the vehicle’s electrical system and maintain battery charge (in this case a high voltage battery).
In the second case, the engine supplies the energy needed to propel the vehicle plus the energy needed to charge the high voltage battery via the E-motor, but at a higher rate, replacing energy taken from battery when in conditions when the E-motor has been operating as an electric motor. This load point shifting makes it possible to operate the engine at a more favorable level of efficiency in the engine load/speed map. The job of hybrid control is now to regulate this alternation of electric driving phases and active charge phases to achieve minimal fuel consumption.
Boosting mode. When the driver consciously activates a request for maximum power (by kickdown or by putting the gearshift lever in “S” position), the E-motor supports the V6 TSI beyond the engine’s full-load curve. The powers and torques of these two motors are then transferred to the front and rear axles by the 8-speed automatic transmission. As previously noted, this briefly makes available a total combined power of up to 275 kW and a maximum torque of 550 Nm.
Torque intervention. Since it can be controlled extremely quickly, the E-motor is also used—in the framework of transient compensation—to make positive and negative torque interventions. For example, when the driver makes a positive load request the E-motor briefly boosts the V6 TSI until it has reached its steady-state target value. This allows the Touareg Hybrid to keep accelerating. Negative torque interventions largely replace classic interventions via the internal combustion engine that are not optimal for efficiency, but are needed for occupant comfort during gear shifting or sudden charge changes.
The specific mode that is activated is shown by an energy flow indicator in the display of the RNS 510 radio-navigation system installed in the prototype vehicle.
The hybrid manager is integrated in the engine controller and communicates via the CAN bus lines with units such as the automatic transmission, high voltage battery and power electronics. The latter also manages the energy flow between the electric motor and battery. Using the DC/DC converter, the power electronics also ensures that the car’s 12V electrical system is supplied via the E-motor or the high voltage battery. Depending on the charge state of the battery (capacity: 6 Ah), vehicle speed and other vehicle-specific parameters, the hybrid manager automatically selects the ideal operating mode based on analysis of all signals.
|Cutaway of the battery pack. Click to enlarge.|
The NiMH battery pack is located in a space saving area. On the prototype, the cargo floor has been raised by 50 millimeters. The battery weighs 67 kilograms, consists of a total of 240 individual cells , with a voltage of 288V. An additional duct integrated in the Touareg’s interior ventilation system and two separate fans are used to keep the battery within an optimal temperature range. A battery manager continually monitors battery charge by coordinating data with the hybrid manager integrated in the engine controller.
The battery system, which includes a Protect Box (in the event of a crash), battery and ventilation components, weighs 79 kg.
To compensate for a portion of the weight of the hybrid components (about 175 kg, or 386 lbs), the hybrid prototype has a number of modifications compared to the production vehicle. One example is the full-time 4XMotion all-wheel drive. In the production Touareg, the drive is transferred to the front and rear axles via a transfer box which contains a lockable central differential and a two-speed range gearbox. On the Touareg V6 TSI Hybrid this is replaced by a lighter Torsen differential similar to the one Audi uses on the Q7. All the traditional capabilities of the Touareg are fully preserved, such as its optimal properties as a towing vehicle.
Other differences from the production Touareg include:
The 8-speed automatic transmission was also specifically tuned for hybrid use. Among other things, it received a special torque converter with larger lock-up system, an auxiliary electric oil pump (to maintain a supply of oil when the V6 TSI is switched off), a transmission heater to reach optimal operating temperature faster, and a modified transmission controller.
The prototype has electro-hydraulic power steering, which does not have to rely on a servo pump driven by the internal combustion engine
A high voltage air conditioning compressor guarantees maintains interior temperatures on the Touareg V6 TSI Hybrid, even when the V6 engine is switched off.
Instead of an alternator, the DC/DC converter integrated in the power electronics ensures a constant supply of power to the vehicle electrical system.
The E-motor takes over the role of engine starter motor. As soon as the engine is to be restarted, the transmission’s lock-up torque converter is put in the “Slip” position and the E-motor’s speed is increased to a setpoint value prescribed by the transmission controller. Only then does the engine controller receive an enable to actuate the disengagement clutch.
The E-motor drags up the V6 TSI by subsequent engagement of the clutch and, as soon as the cylinders fill, the engine is started by enabling of injection and ignition. The E-motor’s torque is increased by the amount of the momentary torque transferred by the disengagement clutch during the drag operation and—after the internal combustion engine has started—it is reduced again in response to the increase in engine torque. When positive engagement occurs at the disengagement clutch, the lock-up torque converter is engaged again.
The Touareg V6 TSI Hybrid will be Euro-5 and US ULEV2 compliant.
Passat BlueMotion. A new common rail TDI (81 kW / 109 hp) delivers 4.9 L/100km (48 mpg US) average fuel consumption and CO2 emissions of 128 g/km (wagon: 129 g/km). The Passat BlueMotion has a stop-start system as standard equipment and meets Euro-5 requirements that take effect in September. Also new in the technology package are: longer gear ratios; low-friction drive shafts; super reduced rolling resistance tires and extra lightweight wheels made of flow-formed steel. The material thickness of these wheels is lower in certain sections to save on weight. This car is already being sold.
Passat BlueTDI. This will be the first TDI launched by Volkswagen to meet the Euro-6 emissions standard that does not become law until 2014. A SCR catalytic converter reduces NOx to less than 80 mg/km. Production of the 2.0-liter, 105 kW (141 hp) Passat BlueTDI will ramp up at the beginning of March. Fuel consumption of the sedan with standard 6-speed transmission is 5.2 L/100km (45 mpg US), with CO2 emissions of 137 g/km (wagon: 5.5 L/100km and 144 g/km CO2). As an option, the Passat BlueTDI is available with a 6-speed DSG. The Passat BlueTDI is positioned above the Passat BlueMotion due to its greater power and more sophisticated emissions control system.
Passat TSI EcoFuel. The 110 kW (148 hp) TSI EcoFuel is boosted by supercharger and turbocharger and accelerates to 100 km/h in 9.7 seconds. Equipped with a 7-speed dual clutch transmission (DSG), it requires 4.4 kilograms of natural gas per 100 kilometers, with 119 g/km CO2. Market launch for both the Passat and Passat Wagon TSI EcoFuel is already scheduled for the first part of 2009.